GABA_Aand GABA_Breceptors of distinct properties affect oppositely the proliferation of mouse embryonic stem cells through synergistic elevation of intracellular Ca²⁺

Abstract

Gamma-amminobutyric acid (GABA), the major inhibitory neurotransmitter in the central nervous system of vertebrates, serves as an autocrine/paracrine signaling molecule during development, modulating a number of calcium (Ca(2+))-dependent processes, including proliferation, migration, and differentiation, acting via 2 types of GABA receptors (GABARs): ionotropic GABA(A)Rs and metabotropic GABA(B)Rs. Here, we demonstrate that mouse embryonic stem cells (mESCs), which possess the capacity for virtually unlimited self-renewal and pluripotency, synthesize GABA and express functional GABA(A)Rs and GABA(B)Rs, as well as voltage-gated calcium channels (VGCCs), ryanodine receptors (RyRs), and inwardly rectifying potassium (GIRK) channels. On activation, both GABAR types triggered synergistically intracellular calcium rise. Muscimol (a GABA(A)R agonist) induced single Ca(2+) transients involving both VGCC-mediated Ca(2+) influx and intracellular stores, while baclofen (a GABA(B)R agonist) evoked Ca(2+) transients followed by intercellular Ca(2+) waves and oscillations that were resistant to antagonists and entirely dependent on Ca(2+) release from intracellular stores. Prolonged treatment with muscimol slightly inhibited, while baclofen or SR95531 (a GABA(A)R antagonist) significantly facilitated, mESC proliferation. GABA(A)R-specific ligands also induced morphological and gene expression changes indicating a differentiation shift. Our data suggest that the interplay between GABARs and downstream (coupled) effectors differentially modulates mESC proliferation/differentiation through selective activation of second messenger signaling cascades.-Schwirtlich, M., Emri, Z., Antal, K., Máté, Z., Katarova, Z., Szabó, G. GABA(A) and GABA(B) receptors of distinct properties affect oppositely the proliferation of mouse embryonic stem cells through synergistic elevation of intracellular Ca(2+).

GABA Promotes Human β-Cell Proliferation and Modulates Glucose Homeostasis

“…3A). This is consistent with previous findings that activation of GABA B R results in a rise in Ca 2+ concentration that, however, is released from intracellular Ca 2+ stores (19). We conclude that GABA increases intracellular Ca 2+ in human b-cells through the activation of both GABA A R and GABA B R. To determine whether GABA-induced intracellular Ca 2+ is linked to a secretory event, we performed glucose-stimulated insulin secretion in isolated human islets.…”

“…GABA B R is a G-protein-coupled receptor consisting of two nonvariable subunits, and upon activation it initiates cAMP signaling and Ca 2+ -dependent signaling. Of note, previous studies demonstrated that under membrane depolarizing conditions, activation of GABA A R triggered voltage-gated calcium channel-dependent Ca 2+ influx and Ca 2+ release from intracellular stores, whereas GABA B R activation evoked intracellular Ca 2+ only (19). Our observations that the GABA B R-mediated activation of the cAMP-PKA signaling is independent of the PI3K-Akt pathway appear to be of physiological relevance.…”

Calcium signaling in human pluripotent stem cells

“…Calcium signals in hESC-derived cardiomyocytes and neural cell types have been measured in most cases by calcium sensitive dyes: for cardiomyocytes Fura-2/AM [25][26][27][28], Fluo-4/AM [29,30] or dsRed+ [27], while for neural cell types Fluo-3/AM [8,31] Fura-2/AM [8,32] or Oregon green 488 Bapta-1 AM [33] have been applied. In pluripotent cells the application of Fluo-3/AM (mESC- [34], hESC- [8]) or Fluo-4/AM (mESC- [35][36][37], and hESC [12]) has been reported. The application of GECIs, while already widely reported in various functional studies, has only been described in mPSCs [38] and in hPSCs, as well as in their differentiated offsprings (see Apati et al [39]).…”

The role of Ca2+ signaling on the self-renewal and neural differentiation of embryonic stem cells (ESCs)

“…For example, epidermal growth factor (EGF) has been shown to promote the proliferation of mouse E14TG2a ESCs via the phosphorylation of connexin 43, which involves an influx of Ca 2+ and translocation of protein kinase C (PKC), along with the subsequent downstream activation of p44/42 and p38 mitogen activated protein kinase (MAPK) pathway [27]. In addition, agonists of -aminobutyric acid A (GABAA) and GABAB receptors can trigger the differential rise of intracellular Ca 2+ and the interplay between the downstream effectors to modulate the proliferation of mouse R1 ESCs [28]. Furthermore, ligands such as adenosine triphosphate (ATP) and lysophosphatidic acid (LPA), are known to stimulate the proliferation of E14TG2a and D3 ESCs by triggering a release of Ca 2+ via the phospholipase C (PLC)/PKC/IP3 pathway [29] [30].…”